In the field of ore processing, activated carbon is commonly used to adsorb and recover precious metals such as gold. Both carbon-in-pulp (CIP) and carbon-in-leach (CIL) processes are commonly used where activated carbon is injected into adsorption tanks after leaching gold ore with cyanide. A typical gold extraction system involves several large agitated tanks oriented in either a horizontal series or cascade system. Alkaline slurry moves downstream from tank to tank and activated carbon is introduced into the system moving upstream. The loaded activated carbon is then extracted from the slurry via some sort of screening apparatus and pumped out of the system.
These methods of gold recovery are time consuming and require continuous operation to be most effective. Unfortunately, existing screening apparatuses have many disadvantages. Most systems use a metal drive chain to rotate a vertically disposed rotary screen cage. The drive chains are metal and are exposed to alkaline solutions causing chemical breakdown in addition to the normal mechanical wear which requires frequent maintenance and replacement. Another common problem is that these screens frequently become irreversibly pegged or blinded by particulate matter as material clogs the screening material. Blinding occurs when wet material clumps up and sticks to the screen surface. This can result in a significant loss of screen open area resulting in a decrease in flow capacity. These screening apparatuses are adversely affected by the lower flow rates created by the clogged screens. These apparatuses require full flow of the slurry or pulp to maintain solids in suspension, so phase separation can occur when in a low or no flow condition decreasing efficiency. The only way to unclog the system requires frequent time consuming manual removal and cleaning of the screening material resulting in lost production.
Consequently, there exists a need for an apparatus that is useable in with both CIP and CIP processes that circumvents the known problems and is more efficient at removing the loaded activated carbon from the slurry. The present invention discloses an apparatus for separating course solid particles from a slurry solution without drive chain wear or frequent blinding. This invention decreases the cost of the frequent maintenance inherent in known systems and allows the processes of gold recovery to continue without interruption improving efficiency.